The present invention relates to the field of rotating machinery and to systems for mechanically mounting an element to a shaft. More specifically, the invention relates to an innovative hydraulically positioned shaft bearing attachment system used to mount a bearing assembly to a shaft.
Rotary mechanical systems include elements, such as bearings, that allow relative rotational movement between respective parts. For example, a rotary system might include a stationary housing that supports a rotating shaft via a bearing assembly. The bearing assembly is typically mounted directly to the shaft and allows for the relative rotational movement between the stationary housing and the rotating shaft.
A variety of mounting systems are known and commercially available for mounting a bearing assembly or other mechanical element to a shaft. Some of these systems make use of a tapered sleeve that fits snuggly between the outer periphery of the shaft and the inner ring of the bearing assembly. The tapered outside diameter of the sleeve engages the tapered inside diameter of the bearing assembly and causes the sleeve to enter into an interference fit with both the inner ring and the shaft. Variations of this type of arrangement may include multiple sleeves that alleviate the need for a taper either on the shaft or the bearing ring, as well as various mechanical arrangements for pressing or drawing the sleeve into tight engagement.
Those skilled in the art are familiar with the operation of this type of system and the limitations of using such systems. A first limitation relates to part tolerance and the initial clearance between these parts (i.e., the shaft outside diameter, the sleeve width, the inside diameter of the bearing assembly, etc.). These are inherent in every mechanical system because each component is manufactured within some tolerance range and each assembly has some initial clearances to allow the user to assemble and initially position the parts. In bearing mounting arrangements, the user can eliminate this variable by assembling the parts to an initial position or “zero reference point” that represents the position where all of these tolerances and initial clearances between the parts have been removed. This initial position can be problematical in that, if not accurately established, it can lead to further assembly problems as discussed below. No current bearing mounting system provides an easy, reliable, and consistent method to determine this initial position.
Besides the tolerance and initial clearance between all of the mating parts, bearing assemblies themselves have an initial internal clearance between the internal components of the bearing. Too much, and particularly too little internal clearance, such as resulting from overloading the internal ring, can result in damage to the bearing and eventual mechanical system failure. Tapered sleeve arrangements can overload bearings, effectively reducing the internal clearance by expanding the inner ring of the bearing. In current bearing mounting systems, it may be difficult to determine exactly how much inner ring expansion might occur during the assembly process.
Another limitation of tapered sleeve mounting systems relates to the manner in which the tapered sleeve is driven or drawn into engagement between the bearing assembly and the shaft. Often in such systems, a drive thread is used to urge the tapered sleeve into place. This drive thread is often incorporated into the outside diameter of the sleeve itself, thus requiring the thread to be no less than the shaft diameter. Because these systems can be used on very large shaft diameters (e.g., 10 inches and larger), the threads themselves must also be relatively large. Consequently, special tooling is often required to torque the larger components that engage the oversized threads. Furthermore, this tooling does not solve the problem of accurately determining the initial position.
A further issue with existing bearing mounting systems is that large diameter threads have larger contacting areas and thus frictional losses are increased. This is, of course, particularly problematic for large shaft and bearing sizes. These forces, when combined with the frictional forces of the tapered system itself, result in very large moments that must be imparted on the components to thread the sleeve properly into engagement. Also, those skilled in the art will appreciate that the frictional force in this thread can vary greatly resulting in a great deal of uncertainty in the torque required to engage the sleeve in place. This is problematic because this torque value is often used to determine the initial position and/or the fully engaged position. If this torque is not consistent, the proper positioning of the sleeve will be uncertain.
Another limitation of tapered sleeve mounting systems relates to the force required to extract the sleeve from between the bearing assembly and the shaft. As discussed above, the tapered sleeve is driven into the bearing assembly using a drive mechanism that may expand the inner race of the bearing, thus creating contact stress between the parts. In large diameter bearing systems (e.g., 10 inches and larger), this contact stress can be very high, requiring a great deal of force to disengage the sleeve from the bearing assembly. Some mounting systems require the user to overcome this force manually, making it extremely difficult for the user to disengage the bearing from the shaft.
There is a need in the art for techniques for securing rotating components, particularly bearings and shafts, that alleviate or address at least some of these drawbacks of existing technology. There is a particular need for an approach in the assembly of sleeve systems that allows for accurate judgment of initial and final engagement of a sleeve between a bearing and a shaft, or between any two concentrically mating elements. Furthermore, there is a need for a system that is less physically tasking on the user in order to complete the installation.